This invention pertains to anti-erosion protrusions provided on wear surfaces exposed to abrasive action and wear from an erosive flowing medium, such as within fluid-carrying conduits. It pertains particularly to such anti-erosion protrusions having specific shapes and patterns and attached to the radial outer portion of the interior surface of elbows to provide anti-erosion protection for the surface.
Protrusions have been used within conduits as a means for distributing fluid flow. For example, the distribution of the heavier particles of a coal-air mixture leaving a pulverizer exhauster vary with capacity, and protrusions have been used within conduits as a mechanical means to evenly distribute the coal flow to various conduits located downstream from the exhauster. However, at the time these protrusions were used, the flow velocities were low so that interior surface abrasion was not a problem.
The undesired erosion in fluid-carrying conduits handling abrasive particulate solids such as coal, sand, etc., has been combated by using various hard materials such as cast iron, ni-hard iron, stainless steel, and similar materials having a relatively high Brinell hardness number. Also, cladding the conduit interior surface with various ceramic or metallic patches which provide a coating of a hard abrasive-resistant material have been tried. One arrangement has been the use of abrasion-resistant ceramic materials, such as nitrite bonded silicon carbide, dense alumina, or fused cast alumina, bonded to the conduit inner surface. Although such uses of bonded ceramic materials are effective, the thickness requirements for the ceramic material and its bonding agent result in increased weight for the metal conduit and accompanying increased costs. Other disadvantages for such use of ceramics are the difference in thermal expansion coefficients between the ceramic material and the outside metal conduit or container, and the potential for their breakage from thermal shock during operations.
Some, limited use of protrusions in fluid conduits and pipes for specific purposes is generally known. For example, U.S. Pat. No. 1,518,705 to Raun discloses a pipe and elbow configuration having longitudinal corrugations cast integrally into the interior surface to provide a wearing surface for flowing particulate materials. U.S. Pat. No. 2,834,059 to Hoelzel discloses a pneumatic bulk transport system for handling bulk fibrous insulation material, and having a plurality of pins or teeth extending inwardly from the conduit wall in a staggered relationship to facilitate flow control and avoid accumulations of the fibrous material. Also, U.S. Pat. No. 3,924,901 to Phillips discloses a particle build-up suppressor having various shaped fin projections located on the inner surface of an elbow for particle deflection and separation purposes, however, no erosion prevention capability is disclosed. Thus, further improvements are needed in providing anti-erosion protection for the interior surfaces of fluid conduits, particularly for elbows handling abrasive and/or erosive materials such as airborne coal particles and hot flue gases carrying particulate ash solids. Such improvements in anti-erosion protection have been advantageously provided by this invention.